I found 4 lab cases where this happens if the amount of data backed up is greated than 2TB. Is your backup going to be this large?
If so, there is a fix available for this. You will need to open a case with the response center, run a debug for them to make sure that it is teh same problem, and you will be sent a test binary
When opening the case (if the amount of data to be backed up is more than 2TB), refer to QCCR2A50372
It appears one thing the upgrade to 7.03 did accomplish is to take care of the original error